Aaron: Imagine that you are walking up a softly sloping suburban street and a child's ball goes rolling by. Your first thought would be that it had gotten away from a child at play. If there were no child about, you might imagine that it had been set rolling by the wind and gathered speed when it reached the sloped sidewalk, or that some animal, a dog perhaps, had moved it from its rest. Under no condition would you imagine that this ball, for no reason what so ever, had simply left its resting place and begun to roll down the street. That would be ridiculous.
An object at rest tends to stay at rest. That is one of the most important laws of Newtonian physics. When ever we see an object in motion, be it a ball or an airplane, even the sun in the sky, we must assume that something set it in motion. Let us imagine that the ball rolling down the street had gotten away from a small boy. The boy had kicked the ball while playing a game with some friends. The kick had come at the command of certain nerve fibers in his nervous system. The command to kick came from his desire to kick the ball. His desire to kick the ball came from his want to play the game. The game arose because the friends got together. The friends got together because they have common interests. They have common interests because they live near to each other. They live near to each other for many reasons, their father's occupation, perhaps. This chain can be traced back farther and farther until we get to the reason for their being born, the reason for their parents and their parents' parents being born, and, if we care to take the time, to the beginning of time itself. For every action in every life in that chain there is a reason, because there can be no action without cause.
There is nothing illogical about the series of actions I have just outlined, but one problem does arise. Since every motion or action requires something to initiate it, this chain would have to go on forever. The only way that we can avoid this ridiculous state of affairs is for us to assume that there is something that started the whole process in the first place, something that exists without cause. That something is God.